Block copolymers of monoalkenyl arenes and conjugated dienes are well known. For example, the preparation of linear styrene-conjugated diene-styrene block copolymers were taught in U.S. Pat. No. 3,149,182 and coupled, radial (styrene-conjugated diene)nX block copolymers were taught in U.S. Pat. No. 7,625,979. These highly engineered materials are most readily prepared by anionic polymerization. Not all monomeric materials are suitable for such polymerization and, as such, prior developments have focused on anionic block copolymers comprising monoalkenyl arenes such as styrene and conjugated dienes such as butadiene and isoprene. Using this limited set of monomer building blocks a wide variety of materials having a broad range of properties have been made by varying, for example, the sizes of the blocks, the relative amounts of each block, and the arrangement of blocks within the copolymer.
Monomers derived from petrochemicals, like isoprene and butadiene, suffer from recurrent shortages and lack of sustainability. It is important to consider bio-derived monomers which can help reduce the need for petro-derived monomers. Terpenes are naturally occurring products that can be found in or synthesized from natural sources. Such terpenes include myrcene (C10 H16). While myrcene is currently an expensive diene, its cost can be mitigated by employing a less costly diene in a copolymer diene block with myrcene. This practical approach allows construction of economically interesting materials maintaining the new properties inherent in myrcene block copolymers.
The need continues to exist for styrenic block copolymers that have properties similar or superior to styrene-isoprene-styrene or styrene-butadiene-styrene block copolymers. One way to achieve this is to incorporate a new monomer in the block copolymer. This leads to a different balance in properties which was not achieved before. The present invention addresses this need.